/*************************************************************************
**                                                                      **
**      A E S 1 2 8  -  AES-128 encryption and decryption				**
**                                                                      **
**      Copyright 2008 Yubico AB										**
**                                                                      **
**      Date		/ Sig / Rev  / History                              **
**      2008-06-05	/ J E / 0.00 / Main									**
**                                                                      **
*************************************************************************/

#include "aes128.h"
#include <string.h>

#define	NUMBER_OF_ROUNDS	10

static const unsigned char RC[] = 
	{ 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };

static const unsigned char sbox[] = {
  0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 
  0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 
  0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 
  0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 
  0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 
  0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 
  0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 
  0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 
  0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 
  0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 
  0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 
  0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 
  0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 
  0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 
  0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 
  0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 
  0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 
  0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, 
  0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 
  0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 
  0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 
  0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 
  0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 
  0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 
  0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 
  0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 
  0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 
  0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 
  0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 
  0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 
  0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 
  0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};

static const unsigned char inv_sbox[] = {
  0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 
  0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 
  0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 
  0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 
  0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 
  0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 
  0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 
  0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 
  0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 
  0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 
  0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 
  0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 
  0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 
  0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 
  0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 
  0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 
  0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 
  0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 
  0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 
  0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 
  0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 
  0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 
  0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 
  0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 
  0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 
  0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 
  0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 
  0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 
  0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 
  0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 
  0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 
  0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
};

static unsigned char xtime(unsigned char b) { 
	return (b & 0x80) ? ((b << 1) ^ 0x1b) : (b << 1); 
}

/*************************************************************************
**  function aesEncrypt													**
**  Encrypts a single AES-128 block										**
**                                                                      **
**	void aesEncrypt(unsigned char *state, const unsigned char *key)		**
**                                                                      **
**  Where:                                                              **
**	"state" is state buffer, i.e. plaintext in, ciphertext out			**
**	"key" is pointer to AES key											**
**                                                                      **
*************************************************************************/

void aesEncrypt(unsigned char *state, const unsigned char *key)
{
	unsigned char i, j, k, tmp, round_key[0x10];

	memcpy(round_key, key, sizeof(round_key));

	for (i = 0; i < 16; i++) state[i] ^= key[i];

	for (i = 0; i < NUMBER_OF_ROUNDS; i++) {

		// byte_sub_shift_row(state);

		/* First row: 0 shift, 0 4 8 12 */
		state[0] = sbox[state[0]];
		state[4] = sbox[state[4]];
		state[8] = sbox[state[8]];
		state[12] = sbox[state[12]];

		/* Second row: 1 shift, 1 5 9 13 */  
		tmp = state[1];
		state[1] = sbox[state[5]];
		state[5] = sbox[state[9]];
		state[9] = sbox[state[13]];
		state[13] = sbox[tmp];

		/* Third row: 2 shift, 2 6 10 14 */
		tmp = state[2];
		state[2] = sbox[state[10]];
		state[10] = sbox[tmp];
		tmp = state[6];
		state[6] = sbox[state[14]];
		state[14] = sbox[tmp];

		/* Fourth row: 3 shift, 3 7 11 15 */
		tmp = state[15];
		state[15] = sbox[state[11]];
		state[11] = sbox[state[7]];
		state[7] = sbox[state[3]];
		state[3] = sbox[tmp];

		if (i != (NUMBER_OF_ROUNDS - 1)) {

			// mix_column(state);

			for (k = 0; k < 16; k += 4) {

				j = state[k] ^ state[k + 1];				
				tmp = j ^ state[k + 2] ^ state[k + 3];
    
				j = xtime(j);

				state[k] ^= (j ^ tmp);

				j = state[k + 1] ^ state[k + 2];
				j = xtime(j);

				state[k + 1] ^= (j ^ tmp);

				j = state[k + 2] ^ state[k + 3];
				j = xtime(j);

				state[k + 2] ^= (j ^ tmp);    
				state[k + 3] = state[k] ^ state[k + 1] ^ state[k + 2] ^ tmp;
			}
		}

		round_key[0] ^= RC[i];

		round_key[0] ^= sbox[round_key[13]];
		round_key[1] ^= sbox[round_key[14]];
		round_key[2] ^= sbox[round_key[15]];
		round_key[3] ^= sbox[round_key[12]];

		for (k = 4; k < 16; k++) round_key[k] ^= round_key[k - 4];

		// add_round_key(state, round_key);

		for (j = 0; j < 16; j++) state[j] ^= round_key[j];
	}
}

/*************************************************************************
**  function aesDecrypt													**
**  Decrypts a single AES-128 block										**
**                                                                      **
**	void aesDecrypt(unsigned char *state, const unsigned char *key)		**
**                                                                      **
**  Where:                                                              **
**	"state" is state buffer, i.e. ciphertext in, plaintext out			**
**	"key" is pointer to AES key											**
**                                                                      **
*************************************************************************/

void aesDecrypt(unsigned char *state, const unsigned char *key)
{
	unsigned char i, j, round_key[0x10];
	unsigned char a02x, a13x;
	unsigned char a02xx, a13xx;
	unsigned char k1, k2;

	memcpy(round_key, key, sizeof(round_key));
	for (i = 0; i < NUMBER_OF_ROUNDS; i++) {
		round_key[0] ^= RC[i];

		round_key[0] ^= sbox[round_key[13]];
		round_key[1] ^= sbox[round_key[14]];
		round_key[2] ^= sbox[round_key[15]];
		round_key[3] ^= sbox[round_key[12]];

		for (j = 4; j < 16; j++) round_key[j] ^= round_key[j - 4];	
	}
	for (i = 0; i < 0x10; i++) state[i] ^= round_key[i];

	for (i = 1; i <= NUMBER_OF_ROUNDS; i++) {
		// inv_byte_sub_shift_row();
		
		/* First row: 0 shift, 0 4 8 12 */
		state[0] = inv_sbox[state[0]];
		state[4] = inv_sbox[state[4]];
		state[8] = inv_sbox[state[8]];
		state[12] = inv_sbox[state[12]];

		/* Second row: -1 shift, 1 5 9 13 */  
		j = state[13];
		state[13] = inv_sbox[state[9]];
		state[9] = inv_sbox[state[5]];
		state[5] = inv_sbox[state[1]];
		state[1] = inv_sbox[j];

		/* Third row: -2 shift, 2 6 10 14 */
		j = state[2];
		state[2] = inv_sbox[state[10]];
		state[10] = inv_sbox[j];
		j = state[6];
		state[6] = inv_sbox[state[14]];
		state[14] = inv_sbox[j];

		/* Fourth row: -3 shift, 3 7 11 15 */
		j = state[3];
		state[3] = inv_sbox[state[7]];
		state[7] = inv_sbox[state[11]];
		state[11] = inv_sbox[state[15]];
		state[15] = inv_sbox[j];

//		get_inv_round_key(i);

		for (j = 15; j > 3; j--) round_key[j] ^= round_key[j - 4];

		round_key[0] ^= (RC[NUMBER_OF_ROUNDS - i] ^ sbox[round_key[13]]);

		round_key[1] ^= sbox[round_key[14]];
		round_key[2] ^= sbox[round_key[15]];
		round_key[3] ^= sbox[round_key[12]];

		for (j = 0; j < 16; j++) state[j] ^= round_key[j];
		if (i != NUMBER_OF_ROUNDS) {
			
			//inv_mix_column();

			for (j = 0; j < 16; j += 4) {
				k1 = state[j] ^ state[j + 2];
				a02x = xtime(k1);
				k2 = state[j + 1] ^ state[j + 3];
				a13x = xtime(k2);
				
				k1 ^= (k2 ^ xtime(state[j + 1] ^ state[j + 2]));
				k2 = k1;

				a02xx = xtime(a02x);
				a13xx = xtime(a13x);

				k1 ^= (xtime(a02xx ^ a13xx) ^ a02xx);
				k2 ^= (xtime(a02xx ^ a13xx) ^ a13xx);

				state[j] ^= (k1 ^ a02x);
				state[j + 1] ^= k2;
				state[j + 2] ^= (k1 ^ a13x);
				state[j + 3] ^= (k2 ^ a02x ^ a13x);
			}
		}

	}
}
